Body Composition methodology has received intense and effective technology augmentation in the past five years. The development of whole body in-vivo neutron activation analysis (IVNAA) is the most dramatic addition, Short of cadaver analysis, IVNAA sets an ultimate standard for measuring body composition in-vivo, thus avoiding the time-honored but limiting assumptions of constant hydration (total body water method) and constant lean body density (underwater weighing). Also new and potentially powerful in application are dual photon absorptionmetry (DPA), bioimpedance analysis (BIA), and total body electrical conductivity (TOBEC): each of these new methods adds a new dimension of measurement, because each depends on a fundamentally different physical principle. The current project (Rosetta I) cross comparing these methods in 336 whites ages 20 and up, is 80% complete. The new mapping of all available measurements in the same subjects (a 10% sample will have IVNAA) provides in addition a rich list of new findings: lean body density varies from well above to well below 1.1 g/cc, falling with age, especially in females; DPA estimates of calcium and of fat content correlate remarkably with the more elaborate and expensive IVNAA; and both BIA and TOBEC closely predict body water. Also, a pilot study in blacks shows higher bone density, higher lean body density, and higher potassium than in whites. These results indicate that models obtained in whites certainly can not be extrapolated to blacks, and probably should not be applied to other ethnic groups without explicit validation. This project will extend the same measurements to 672 blacks and Asian groups for which ethnicity are well defined. This well provide extensive new data for populations with high prevalence and morbidity of illnesses with strong body composition factors, such as hypertension, obesity, and diabetes. This study will open new opportunities in body composition.